<%--
  Created by IntelliJ IDEA.
  User: zl0808zf
  Date: 2024/11/29
  Time: 12:57
  To change this template use File | Settings | File Templates.
--%>
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html><body>
<form action="${pageContext.request.contextPath}/welcome.jsp">
  <c:if test="${empty param.num1}">
    name：<input type="text" name="num1">
    <input type="submit" value="submit" /><br />
  </c:if>

  <c:if test="${not empty param.num1}">
    ${param.num1}<br />
  </c:if>
</form>
</body></html>
